Eek! It keeps changing!
Switching things around the other way is an improvement. However, it now means that the individual discussion pages have scroll bars at 1024px width (caused by the new "vote up/down" controls), which is not a good thing.
As we get a lot of more mature readers here, whose visual acuity might not be the best, I'd suggest making sure the forum works at 800px wide too.

Initial impressions: this new forum is more structured towards an initial posting with a few comments, rather than an ongoing discussion. Noticeably absent is a way to get to the most recent unread comments.

Not sure why you say that it's not structured for ongoing discussion. Are you referring to this Activity section?
If you click on Discussions, you will see all the threads from the different forums combined to show the discussions sorted by most recent activity and it will show you how many new posts there are under the title.